A process is an instance of a program running in a computer. It is close in meaning to task , a term used in some operating systems. In UNIX and some other operating systems, a process is started when a program is initiated (either by a user entering a shell command or by another program). Like a task, a process is a running program with which a particular set of data is associated so that the process can be kept track of. An application that is being shared by multiple users will generally have one process at some stage of execution for each user.
A process can initiate a subprocess, which is a called a child process (and the initiating process is sometimes referred to as its parent ). A child process is a replica of the parent process and shares some of its resources, but cannot exist if the parent is terminated.
Processes can exchange information or synchronize their operation through several methods of interprocess communication ( IPC ).